Protein blends are becoming a popular choice for protein supplements, and for good reason. This study found that blending whey and casein proteins led to better gains throughout a 10-week training protocol compared to just whey protein alone. This could be due to the combination of the large spike in protein synthesis from whey and the longer duration of elevated protein synthesis from casein. Other blends do not have much research behind them at this point, but combining whey and casein seems to be a good bet.
▪️ Source: Kerksick, C. M., Rasmussen, C. J., Lancaster, S. L., Magu, B., Smith, P., Melton, C., ... & Kreider, R. B. (2006). The effects of protein and amino acid supplementation on performance and training adaptations during ten weeks of resistance training. The Journal of Strength & Conditioning Research, 20(3), 643-653.